Getting Christmas Cactus to Bloom Again
by Connie Holland
Adams Co. Master Gardener
Gettysburg Garden Club
If you own a “Christmas Cactus”, this is the time of year that it should be setting buds to rebloom. These eye candy blooms start as early as November and can continue well into the New Year,
often blooming again in the spring. If yours has not set buds, this article contains tips to encourage reblooming.
What one thinks of as Christmas Cactus is more likely to be Thanksgiving Cactus since it mostly is what is sold around the holidays. Plants that bloom around Thanksgiving are the species Schlumbergera truncata. True Christmas Cactus blooms later into December and comes from the species Schlumbergera x buckleyi, a hybrid produced in the late 1840s in England. In addition to bloom time, one can distinguish between the two by examining their stem segments or “leaves”. Thanksgiving Cactus segments have sides with pointed lobes along the edges while Christmas Cactus segments are smooth sided and have no pointy edges.
Bloom form is another indicator of species difference. True Christmas Cactus blooms have purplish anthers, the pollen bearing part of the flowers, whereas the Thanksgiving Cactus has yellow anthers. Don’t be confused by the purple tipped stigma present is both. This taller single stigma is where incoming pollen gets deposited for fertilization. For the remainder of this article, “Christmas Cactus” will refer to both species.
These plants flower in response to shorter daylight hours. Flowering also is related to nighttime temperatures. Ideal temperature range for flower bud development is between 55 and 60 degrees for a period of six weeks. As long as the temperatures remain in this range, plants will develop buds regardless of daylight hours. To achieve short-daylight induced blooming, place plants in a room that does not have any artificial light source such as lamps. The plants should receive no more than 8-11 hours of light. Plants also can be forced into reblooming each year by using timers to control a shorter light exposure.
During flower bud formation, stop fertilizing and only water enough to keep the leaves from becoming shriveled. Sometimes my plants reward me with a few more blooms again in March or April. My personal observation is that keeping them on the dry side after flowering is a sort of rest period that, when followed by fertilization, invigorates them into blooming again. If one wishes to force blooms any other time of the year, all that is required is to keep the plants cooler and in the dark for 13-16 hours for about four weeks.
One of the most frustrating things that can happen is to have flower buds drop off the plant before they bloom. Several different conditions, usually over-watering, insufficient light, or relocating the plant during early bud development can cause bud drop. Years ago I discovered that moving a plant led to the buds “turning” toward the light source and then falling off! Do not rotate plants while they are forming buds. Leave them alone until the buds are well developed and nearly in bloom. Then the plant can be relocated for viewing enjoyment. I should warn you that any newly purchased plant in bud will most likely drop some buds at home due to the abrupt light source change. Drafts and temperature extremes also can cause buds to drop.
Bloom colors include white, pinky-white, fuchsia with a white throat, fuchsia with a fuchsia throat, red, orangey-red, apricot and yellow. Oddly, white blooming plants will bloom pinkish-white if kept at lower temperatures. For years it was my goal to collect one of each color. I finally succeeded when I obtained a yellow-blooming plant a few years ago. A recent catalogue showed fringed blooming species available for the first time. Christmas Cactus species are long lived and will bloom year after year. Many are even passed down through generations.
These plants are easy to grow and are lovely just as houseplants. They are fairly disease resistant. However, since they are tropical cacti and not desert types, their needs are somewhat different. Bright indoor light intensity or outdoor shade and soil high in organic matter are recommended. Water when the soil surface begins to feel dry. The plant may be kept drier in fall. Any well-balanced fertilizer may be used according to label directions. Try to resist the temptation to repot this plant as it thrives on being pot-bound to flower. If you do repot, do not step up to a larger pot size and wait until the plant stops flowering. Pruning after blooming will encourage the plant to branch. Remove a few sections of each stem by pinching or cutting. These can be rooted in moist potting soil or in water to produce new plants.
These holiday plants, so common and yet so beautiful, are easy to grow and will bloom every year if attention is paid to their requirements. With both Thanksgiving and Christmas approaching, why not get some?